Apparatus and method for descaling a workpiece with a liquid jet

ABSTRACT

A workpiece is moved past a rotor descaling device, which intermittently sprays the workpiece with at least one liquid jet formed intermittently in dependence on angular positions of a rotor rotating on a rotational axis intersecting the surface (23) of the workpiece (22).

BACKGROUND OF THE INVENTION

The invention relates to a process for descaling a workpiece,particularly a rolled piece, wherein the workpiece is moved past a rotordescaling device, where at least one liquid jet rotating on a rotationalaxis intersecting the workpiece surface to be descaled is sprayed ontothe surface to be descaled, with the liquid jet being formedintermittently, i.e. with temporary interruptions, with the liquid jetbeing formed intermittently, i.e. with temporary interruptions, and to arotor descaling device for implementing the process.

DISCUSSION OF RELATED ART

Rotor descaling devices are known, for example, from DE-A-43 28 303 orEP-A-0586 823 or DE-A-31 25 146. These known rotor descaling devices areequipped with spray nozzles which are located at rotating beams orrotating nozzle holders and directed towards the workpiece surface to bedescaled. As a rule, the rotational axis is perpendicular to theworkpiece surface to be descaled.

In this process, liquid admission patterns are formed by individualspray curves in the form of intertwined cycloids according to therelative motion between the workpiece and the rotating spray nozzles,which is dependent on the movement of the workpiece and the nozzlespeed, as well as according to the number of nozzles. As a result,liquid jets are repeatedly admitted to one and the same workpiecesurface. The disadvantage of this process is that the consumption ofsprayed liquid is very high and, thus, the workpiece cools to a lowertemperature than actually required for descaling.

A process for spraying the liquid jets onto the workpiece surface at aninclination against the moving direction of the workpiece is known fromEP-A-0 640 413. According to this document, this process is implementedby covering the liquid jet over that part of its rotational motion whichdoes no longer meet the requirement of being directed against the movingdirection of the workpiece. This process also involves high liquidconsumption even though no the total amount of liquid strikes theworkpiece.

Rotor descaling devices of the aforementioned type are already knownfrom U.S. Pat. No. 5,220,935 and DE-A 23 55 893, according to whichliquid consumption can be reduced by applying an intermittent liquidjet. Furthermore, double admission of liquid jets onto workpiecesurfaces and, thus, unnecessary undercooling of the rolled piece,particularly with a view to a subsequent rolling process, is avoided.

However, this embodiment does not yet allow optimum descaling of aworkpiece at minimum liquid consumption.

A special effect of the process according to the invention is thatpressure peaks occur which are caused by single or repeated interruptionof the liquid jet and lead to elevated jet pressures. As a result, thedescaling effect is essentially improved. The pressures of the liquidjets assume peak values amounting to a multiple of the constant jetpressures known from conventional processes. According to the invention,the impact pressures of the liquid jets on the surface of the workpieceare so high that the liquid pressure can be considerably lowered and animproved descaling effect is achieved.

SUMMARY OF THE INVENTION

The object of the invention is to avoid the described disadvantages anddifficulties and to develop a process and a device for implementing theprocess where the effect of elevated jet pressures resulting fromintermittent formation of the liquid jet is enhanced and distributedover the surface of the workpiece. Furthermore, optimum descaling atminimum liquid consumption is to be achieved. Particularly, not only areduction of liquid consumption but also of the liquid pressure is to beachieved without any deterioration of the quality of the surfaces to bedescaled.

According to the invention, this problem is solved by interrupting theformation of liquid jet twice or several times in succession, however,only for a short period of time, i.e. maximally over a liquid jetrotation of 10°, preferably 5°.

In this process, the liquid jets are expediently simultaneously formed.

A rotor descaling device for implementing the process according to theinvention with a liquid supply line to a stator and a rotor which ispivoted compared with the stator and equipped with at least one nozzlefor the formation of a liquid jet is characterized in that aninterrupting device is provided between the rotor and stator whichallows intermittent liquid supply to a nozzle.

The interrupting device is expediently comprised of a stationary platecam which is rigidly fixed compared with the stator and provided with atleast one control port to allow liquid passage to the nozzle which islimited in time.

A preferred embodiment is characterized in that

the liquid supply line leads into a liquid chamber located at the rotor,

the rotor is provided with a port through which the liquid is conveyedto the nozzle,

one mouth of the port leads into the liquid chamber, and

the port can be intermittently closed by means of the plate cam and iscleared when the mouth of the port is in congruent position with thecontrol port.

A solution providing for a simple design is characterized in that aplurality of ports is provided and that each port leads to one nozzleeach of the rotor, at least two mouths of the ports leading into theliquid chamber at different radial distances from the rotational axis ofthe rotor and the plate cam being provided with a control portcorresponding to a mouth of a port and allowing liquid passage from theliquid chamber to the port.

Several control ports are expediently provided at identical radialdistances from the rotational axis of the rotor, the control portslocated at identical radial distances from the rotational axis of therotor being advantageously combined in groups.

If a liquid jet is to be maintained over a slightly longer distance,i.e. not only in specific points, one control port is designed as acontrol slot extending in circumferential direction of the plate camaccording to a preferred embodiment.

It is particularly advantageous to design the nozzles ascircular-section jet nozzles because higher jet pressures compared withflat-jet nozzles can be achieved thereby since the jet is only minimallywidened at circular-section jet nozzles.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail by several embodimentsshown in the following drawing, where FIG. 1 schematically represents asection through a rotor descaling device, this section being passedthrough the rotational axis. FIG. 2 displays a view of the rotordescaling device in the direction of arrow II, FIG. 3 displays a partialtop view of the rotor hub according to line III--III of FIG. 1, FIG. 4displays a top view of a plate cam according to arrow IV of FIG. 1, FIG.5 displays a spray pattern on a rolled piece represented in top view,and FIG. 6 illustrates the use of rotor descaling devices according tothe invention for particularly wide workpieces, such as continuouslycast slabs, etc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In rotor descaling device 1, rotor 4, which is pivoted in gear housing 2on rotational axis 3, is supported above bearing 6 with its rotor shaft5. To rotor shaft 5, driving pinion 7 meshing with a rotor drive notrepresented in detail is mounted. At the end of rotor shaft 5 projectingoutwards from gear housing 2 rotor hub 8 is located, which is providedwith brackets 9 which radially extend outwards and which carry spraynozzles 10. According to the represented embodiment, twelve brackets 9which are equally distributed along the circumference of rotor hub 8,are provided, one bracket 9 each being equipped with spray nozzle 10.Spray nozzles 10 are designed as circular-section jet nozzles and areconnected with a line to port 11 which extends radially inwards fromspray nozzle 10 through bracket 9 and rotor hub 8.

Rotor shaft 5 is of hollow design and interspersed by hollow tube 12,the so-called stator. This stator 12 projects from gear housing 2 withone end 13, with which is it connected to a fluid line 14, such as ahigh-pressure water line. Between stator 12 and rotor shaft 5 or rotorhub 8, through which stator 12 projects, liquid seals 15 are provided.At end 16 of stator 12 projecting outwards through rotor hub 8 plate cam17 with control ports 18, 18', 18" is mounted, which is permanentlyconnected with stator 12. Both plate cam 17 and stator 12 are coveredwith cover 20 tightly fixed to rotor 8, forming a liquid chamber 19(high-pressure liquid chamber).

As can be particularly inferred from FIG. 4, control ports 18, 18', 18"of the plate cam are located at different radial distances r₁, r₂ and r₃to rotational axis 3 of rotor shaft 5, radial distances r₁ to r₃ beingselected in a way that control ports 18 to 18" can be aligned to mouths21, 21', 21" of ports 11 shown in FIG. 3, which are located inside therotor. This means that ports 11 also extend inwards up to differentradial distances r₁ to r₃ from rotational axis 3 of rotor shaft 5.

According to plate cam 17 displayed in FIG. 4, several control ports 18,18', 18" are provided at identical radial distances r₁ to r₃ ofrotational axis 3 of rotor 4. These control ports may also be combinedin groups, as shown in FIG. 4 for ports 18" which are provided at theshortest radial distance r₁ but may also be designed as bores only, sothat at a rotation of rotor hub 8 on rotational axis 3, inside mouths 21to 21" of ports 11 align only shortly with control ports 18, 18', 18" ofplate cam 17, which is idle during rotation.

According to FIG. 4, control ports 18, 18', 18" are designed as slots sothat mouths 21 to 21" of ports 11, which are located inside the rotationhead, are aligned with control ports 18, 18', 18" over an extendedrotational range.

Rotor descaling device 1 has the following function:

While workpiece 22--according to FIG. 5, for example, a rolled plate anda plate yet to be rolled--with its surface 23 to be descaled is beingmoved on level 24 (cf. FIG. 6) past rotor descaling device 1, whoserotational axis 3 is approximately vertical to this level 24, liquidchamber 19 is pressurized with the liquid to be sprayed on workpiecesurface 23 and rotor 4, i.e. rotor shaft 5 including rotor hub 8, iscaused to rotate, whereby different ports 11 come into line contact withliquid chamber 19 by means of plate cam 17 so that one or severalnozzles 10 are supplied with fluid and, consequently, liquid jets areformed.

The liquid jet is formed as long as control port 18, 18', 18" islinewise connected with the corresponding port 11. If this connection isinterrupted, the liquid jet is also interrupted and does not form againuntil the next control port 18, 18', 18"--or the same control port aftera rotation through 360°--is again linewise connected with port 11. As aresult, an intermittent liquid jet is formed.

Plate cam 17, which is rigidly fixed to stator 12, thus forms aninterrupting device which interrupts the liquid supply to one nozzle 10each at intervals.

An appropriate arrangement of control ports 18, 18', 18" allowsproducing a spray pattern as shown, for example, in FIG. 5. Circularlines 25 illustrate the intermittent liquid jets striking workpiecesurface 23 while the latter is being moved past rotor descaling device ain accordance with the feeding device represented by arrow 26.

When plate cam 17 according to FIG. 4 is used, the outermost section a₃of circular line 25 is supplied by one nozzle 10 each, which are locatedat the largest radial distance r₃ from rotational axis 3 of rotor 4through control slots 18.

Sections a₂ located adjacent to center line 27 of workpiece 22 aresupplied by nozzles 10 through control ports 18' which are located at amean distance r₂ from rotational axis 3, and the three central sectionsa₁ are formed at three closely adjoining control slots 18" which arelocated at the shortest distance r₁ from rotational axis 3 of rotor 4.

It is essential to provide stationary circular arc sections according toFIG. 5 a₁ to a₃ (at zero feed of the workpiece), i.e. the position ofthe sections from a₁ to a₃ is not changed in the direction of rotationbecause the plate cam is idle.

FIG. 6 illustrates the arrangement of several rotor descaling devices 1for large workpiece surfaces 23 as occurring, for example, with slabs orwide strips.

The invention is not limited to the embodiment shown in the drawing butcan be modified in various aspects. For example, nozzles 10 can belocated at different radial distances from rotational axis 3 of rotor 4,and control ports 18, 18', 18" can be arranged in a way that liquid canbe fed to several nozzles 10 at the same time or to nozzles 10individually one after another.

Groups of nozzles can have different nozzle diameters or can becomprised of different nozzle types. As a result, the water supply overthe cross section of the workpiece to be descaled can be kept constant.

What is claimed is:
 1. Process for descaling a workpiece (22),particularly a rolled piece, wherein the workpiece (22) is moved past arotor descaling device (1), with a liquid supply line (14) to a stator(12) and to a rotor (4) which is rotated relative to the stator (12) andprovided with at least one nozzle (10) for the formation of a liquidjet, where at least one temporary interrupted liquid jet rotating on arotational axis (3) intersecting the surface (23) of the workpiece (22)to be descaled is sprayed onto the surface (23) to be descaled,characterized in that the liquid jet is formed intermittently independence on angular positions of the rotor (4), wherein between therotor (4) and the stator (12) an interrupting device (17) is located,which allows intermittent supply of liquid to a nozzle (10).
 2. Processaccording to claim 1, characterized in that several liquid jets areformed, with one liquid jet each being formed by means of a separatenozzle (10) and, during one rotation, allocated to a separate partialarea (a₁ , a₂, a₃) of the surface (23) of the workpiece (22) to bedescaled.
 3. Process according to claim 2, characterized in that theliquid jets are simultaneously formed.
 4. Process according to claim 1,characterized in that the interrupting device is comprised of a platecam (17) which is rigidly fixed compared with the stator (12) andprovided with at least one control port (18, 18', 18") to allow liquidpassage to the nozzle (10) that is limited in time.
 5. Device accordingto claim 4, characterized in thatthe liquid supply line (14) leads intoa liquid chamber (19) provided at the rotor (4), the rotor (4) isprovided with a port (11) conveying the liquid to the nozzle (10), onemouth (21 to 21") of the port (11) leads into the liquid chamber (19),and the port (11) can be intermittently closed by means of the plate cam(17) and is cleared when the mouth (21) of the port (11) is in congruentposition with the control port (18, 18', 18").
 6. Process according toclaim 5, characterized in that a plurality of ports (18, 18', 18") areprovided and that each port (18, 18', 18") leads to one nozzle (10) ofthe rotor (4), with at least two mouths (21) of the ports (18, 18', 18")leading into the liquid chamber (19) at different radial distances (r₁,r₂, r₃) from the rotational axis (3) of the rotor (4) and the plate cam(17) is provided with a control port (18, 18', 18") corresponding to amouth (21) of a port (11) and allowing liquid flow from the liquidchamber to the port.
 7. Process according to claim 6, characterized inthat several control ports (18, 18', 18") are provided at identicalradial distances (r₁, r₂, r₃) from the rotational axis (3) of the rotor(4).
 8. Process according to claim 7, characterized in that the controlports (18, 18', 18") located at identical radial distances (r₁, r₂, r₃)from the rotational axis (3) of the rotor (4) are combined in groups. 9.Process as claimed in claim 4, characterized in that one control port(18, 18', 18") is designed as a control slot extending incircumferential direction of the plate cam (17).
 10. Process as claimedin claim 1, characterized in that the nozzles (10) are designed ascircular-section jet nozzles.